1. Field of the Invention
This invention relates to a lift apparatus for lifting cigarette filter plugs which receives cigarette filter plugs (which are cylindrical rods about 100 mm long to be cut into pieces of a certain length for attachment to cigarettes) fresh from a plug making machine and delivered by a lower horizontal conveyer and conveys the plugs upwardly while as piled in multiple layers to an upper horizontal conveyer.
2. Description of the Prior Art
Generally it is possible in lifting cigarettes from a lower position to a higher position, as seen from Japanese Patent Publication No. 50-10960, to lift the cigarettes by using a parallel pair of vertical conveyers comprising flat belts. In such a prior art construction, a large amount of cigarettes delivered to a bottom portion between the two vertical conveyers is lifted while piled to form layers of a certain thickness between the parallel vertical conveyers. However, where products to be lifted are cigarette filter plugs, those plugs lying centrally of the multilayer pile tend to slip downwardly. It is difficult to carry out efficient lifting of the plugs in multiple layers although the plugs are bar-like products similar to cigarettes in diameter and length. This is due to the following reasons:
Firstly, each plug is produced in the form of a cylindrical rod or bar comprising acetate filter fibers entangled with one another with spot joints formed at contracting paints by softening the fibers with a solvent such as triacetin or the like, with paper rolled around the plug. The fibers softened by the solvent start curing in four or five minutes and cure to a stable hardness after one and one half hours or two hours. Therefore, the plugs immediately after leaving the plug making machine are usually very soft. If such plugs are lifted over a long distance under a strong compacting pressure from both sides imparted by the two parallel vertical conveyers, the plugs will cure in the deformed condition under pressure, which results in intolerable deviations from a truly circular cross-sectional shape. Therefore, the two vertical conveyers cannot have a space therebetween much smaller than the thickness of the plugs in multiple layers nor can they exert a great pinching force on the plugs.
Secondly, the paper rolled around the rod-like filter material is in many instances considerably slicker than the paper material used for cigarettes, and frictional engagements among the plugs are very weak.
For the above reasons it is difficult to lift the fresh made cigarette filter plugs in multiple layers by means of a parallel pair of vertical conveyers comprising flat belts.
Other examples of lift means have been proposed for lifting bar-shaped products such as cigarettes in multiple layers. One of them is shown in Japanese Patent Publication No. 56-31947 in which a parallel pair of vertical conveyers includes a plurality of projections having a triangular cross section attached to the belt surfaces. Another is shown in Japanese Patent Publication No. 46-1199 in which the vertical conveyers comprise porous belts backed by suction boxes. However, the former involves possibility of deforming the plugs with the projections, and the latter has disadvantages of a complicated construction and difficulty in controlling the conveying speed and degree of vaccuum in the suction boxes.
For these reasons, therefore, plugs are lifted in a single layer (namely in a row) on vertical conveyers in filter manufacturing plants today.